improve emcc (#2499)

* improve emcc

* fix envs

* format code

packages/e/emscripten/xmake.lua

@@ -1,5 +1,4 @@
 package("emscripten")
-
     set_kind("toolchain")
     set_homepage("https://emscripten.org/")
     set_description("Emscripten: An LLVM-to-WebAssembly Compiler.")
@@ -10,13 +9,23 @@ package("emscripten")
 
     add_deps("python")
 
+    on_load(function (package)
+        package:addenv("PATH", "upstream/emscripten")
+        package:addenv("PATH", ".")
+        package:addenv("EMSDK", ".")
+        package:mark_as_pathenv("EMSDK")
+        package:mark_as_pathenv("EMSDK_NODE")
+        if package:is_plat("windows") then
+            package:mark_as_pathenv("EMSDK_PYTHON")
+            package:mark_as_pathenv("JAVA_HOME")
+        end
+    end)
+
     on_install("windows", "macosx", "linux", function (package)
         import("lib.detect.find_directory")
 
-		-- copy to installdir
-        os.cp("*", package:installdir())
-
         -- installation
+        os.cp("*", package:installdir())
         local version = package:version():rawstr()
         local installdir = package:installdir()
         local py = package:is_plat("windows") and "python" or "python3"
@@ -26,25 +35,22 @@ package("emscripten")
         os.vrunv(py, {path.join(installdir, "emsdk.py"), "activate", version})
 
         -- setup env
-        package:addenv("PATH", node)
-        package:addenv("PATH", path.join(installdir, "upstream", "emscripten"))
-        package:addenv("PATH", installdir)
-        package:addenv("EMSDK", installdir)
-
         local exe = package:is_plat("windows") and ".exe" or ""
-        local node = find_directory("bin", {path.join(installdir, "node", "**")})
-        if node then
-            package:addenv("PATH", node)
-            package:addenv("EMSDK_NODE", path.join(node, "node" .. exe))
+        local node_bindir = find_directory("bin", {path.join(installdir, "node", "**")})
+        if node_bindir then
+            node_bindir = path.relative(node_bindir, installdir)
+            package:addenv("PATH", node_bindir)
+            package:addenv("EMSDK_NODE", path.join(node_bindir, "node" .. exe))
         end
-
         if package:is_plat("windows") then
             local python = find_directory("*", path.join(installdir, "python"))
             if python then
+                python = path.relative(python, installdir)
                 package:addenv("EMSDK_PYTHON", path.join(python, "python" .. exe))
             end
             local java = find_directory("*", path.join(installdir, "java"))
             if java then
+                java = path.relative(java, installdir)
                 package:addenv("JAVA_HOME", java)
             end
         end